The present invention relates to a method of preparing (trifluoromethyl)pyridine compounds by reacting (trichloromethyl)pyridine compounds with anhydrous hydrogen fluoride in the absence of a catalyst.
Fluorination of (trichloromethyl)pyridine compounds has been carried out by vapor phase fluorination which requires the use of high temperatures. Such vapor phase reactions suffer from disadvantages including, for example, energy costs associated with elevating the temperature of the reactants, the decomposition of starting materials and end products associated with high temperature vapor phase reaction systems and, furthermore, low conversion and/or low selectivities to the desired (trifluoromethyl)pyridine products. See, for example, Japanese Kokai Tokkyo Koho No. 80 85,564, 27 June 1980, Appl. No. 78/158,979, 22 December 1978 and U.S. Pat. Nos. 4,266,064 and 4,288,599.
U.S. Pat. No. 4,184,041 discloses a method of preparing (trifluoromethyl)pyridine compounds by reacting a (trichloromethyl)pyridine compound with gaseous hydrogen fluoride at a temperature from 0.degree.-50.degree. C. While this method may produce small quantities of (trifluoromethyl)pyridine compounds, it is an unacceptable commercial means of producing (trifluoromethyl)pyridine compounds.
It is clearly evident that a more efficient method of preparing (trifluoromethyl)pyridine compounds is desirable in order to commercially produce such compounds.